Econoline E150 1/2 Ton V8-5.4L CNG VIN M (1998)
Compression Check: Testing and Inspection
Interpreting Compression Readings
1. If compression improves considerably, piston rings are faulty.
2. If compression does not improve, valves are sticking or seating improperly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on each piston does not increase compression, the head gasket may
be leaking between cylinders. Engine oil or coolant in cylinders could result from this condition.
Use the Compression Pressure Limit Chart when checking cylinder compression so that the lowest reading is within 75 percent of the highest
reading.
